In recent years, a vertical magnetic recording system has been put to practical use as a means for enhancing the recording density of a magnetic recording medium. A vertical magnetic recording system allows a magnetic film of a magnetic recording medium to be formed in a state that the easy axis of magnetization faces a direction perpendicular to the medium plane, and this is a method adequate for a high recording density, in which even if recording is carried out at an increased recording density, the diamagnetic field within recording bits is small and the recording and playback characteristics undergo less deterioration. In regard the vertical magnetic recording system, there have been developed magnetic recording media each equipped with a magnetic recording film having increased recording sensitivity, and a soft magnetic film.
Regarding the soft magnetic film of such a magnetic recording medium, there is a demand that the soft magnetic film has excellent soft magnetic characteristics, and has an amorphous structure. As an example of the soft magnetic film, use has been made of an alloy film produced by adding elements that promote the formation of an amorphous structure to a Fe—Co alloy containing Fe, which has a high saturation magnetic flux density, as a main component.
Furthermore, such an alloy film is also required to have corrosion resistance. In regard to the formation of an alloy film, for example, a Fe—Co-based alloy sputtering target material for a soft magnetic film, obtained by incorporating one kind or two kinds of elements selected from Nb or Ta into a Fe—Co alloy at a proportion of from 10 atom % to 20 atom %, has been proposed (see, for example, Patent Document 1). Specifically, the Fe—Co-based alloy sputtering target material is produced by mixing pure metal powder raw materials each having a metal purity of 99.9% or higher so as to obtain the composition of the sputtering target material, and sintering the mixed powder thus obtained.